The connection of a component in a waveguide transmission system generally results in some degree of impedance discontinuity which causes undesirable reflected waves. It is well known in the prior art to attempt to tune out these reflected waves by means of a reflecting element which can be adjustably inserted into the waveguide. In cases where the tuning is required over a range of frequencies, more than one such reflecting element may be used. For example, a common technique is to utilize as many as five or more micrometer-driven stub tuners, spaced along the waveguide, to achieve tuning over a frequency range of 12.4 to 18 GHz. Tuning in this manner requires multiple operations, adjusting and readjusting each tuner, and even then complete cancellation of the reflected wave can rarely be obtained.
In U.S. Pat. No. 2,758,287 (Jacobson et al) there is described a single tuner which takes the form of a reflecting plate supported on a dielectric rod which is both rotatable and axially translatable in the waveguide. Translation of this tuner in a direction parallel to the axis of the waveguide results in changes in the phase of the reflected wave. Rotation of the reflecting plate about the translation axis results in changes in the reflected wave magnitude. In theory, the Jacobson et al approach provides a simple and effective way to achieve full cancellation of the reflected wave.However, in practice it is found that rotation of the rod without attendant translation, or translation with attendant rotation, is difficult to achieve. A similar device is disclosed in U.S. Pat. No. 3,518,580 (Hartman), this device also having the same practical limitation of not being able to keep the phase and magnitude adjustments independent of one another.
It is therefore an object of the present invention to provide a technique which permits simple effective and complete tuning in a waveguide transmission system for the purpose of cancelling out reflected waves. More specifically, it is an object of the present invention to provide a tuning arrangement which takes advantage of the simplicity affored by the aforesaid Jacobson et al and Hartman arrangements and yet which permits independent adjustment of the phase and magnitude of a cancelling wave.